Percutaneous transluminal angioplasty has been practiced widely, for example, for treatment of stricture or obstruction of vascular lumen by enlargement and for recovery or improvement of blood flow in coronary and peripheral blood vessels. The balloon catheter used in the percutaneous transluminal angioplasty has a shaft and a balloon inflation and deflation freely by regulation of its internal pressure that is connected to the terminal region of the shaft, and the shaft generally has a structure in which a lumen (guide wire lumen) for inserting a guide wire and a lumen for supplying a pressurized fluid for regulation of the balloon internal pressure (inflation lumen) are formed in the shaft in the length direction.
The PTCA by using such a balloon catheter is generally practiced as follows: First, a guide catheter is inserted from a puncture site such as femoral artery, brachial artery, or radial artery, while the distal end is fed via aorta into the entrance of coronary artery. Then, a guide wire inserted in the guide wire lumen is fed beyond the stenotic lesion of coronary artery, and a balloon catheter is then inserted along the guide wire, while the balloon is delivered to the stenotic lesion. Then, the stenotic lesion is dilated and treated by expansion of the balloon by supply of a pressurized fluid via the inflation lumen by a device such as inflator. After completion of the treatment of the stenotic lesion by dilation, the PTCA is completed by contracting the balloon under reduced pressure and withdrawing it out of the body.
In the cases of a lesion significantly higher in the degree of stricture or of chronic complete obstruction, it is occasionally difficult to treat the lesion by advancing the guide wire beyond the stenotic lesion. In such a case, a penetrating catheter is used, and the guide wire is sent beyond the stenotic lesion.
It is often necessary to administer a treatment substance locally to the stenotic lesion during PTCA. An example thereof is the treatment for dissolving thrombus by local administration of a thrombolytic agent. In such a case, an injection catheter is used for local administration of the treatment substance.
Each catheter described above has a structure in which a distal-end-sided shaft and a proximal-end-sided shaft are connected to each other and a hub holding the catheter is connected to the proximal end of the proximal-end-sided shaft, and such catheters are divided roughly into two groups, depending on the length of the guide wire lumen. Hereinafter, a common balloon catheter having a balloon connected to the distal end side of a distal-end-sided shaft and to the hub and a port for supplying a pressurized fluid for regulation of the internal pressure of the balloon will be described as an example.
An example of the catheter is an over-the-wire catheter (OTW catheter) shown in FIG. 1, in which a guide wire lumen is formed over the entire length of the catheter, a proximal opening of the guide wire lumen is formed in the hub, and a distal opening of the guide wire lumen is formed in the most distal end region or at a position to the terminal side of the most distal end region. Another example thereof is a rapid exchange catheter (RX catheter) shown in FIG. 2, in which a guide wire lumen is present only in the distal end side of balloon catheter and a proximal opening of the guide wire lumen is formed in the middle of the distal-end-sided shaft. Because the OTW catheter has a guide wire lumen over the entire length of the balloon catheter, it is often used for sending a guide wire to the lesion that prohibits passage of the guide wire, but the operation of withdrawing the balloon catheter while leaving the guide wire in the lesion is rather complicated and causes problems. Thus, the OTW catheter demands additional special device and operation such as insertion of an exchange extension wire for withdrawal of the balloon catheter while the guide wire is left in the lesion.
On the other hand, in the RX catheter, the guide wire lumen is present only in the distal end side of the balloon catheter; thus, the convenience of operation is very favorable, as it is possible to remove, exchange, reinsert the balloon catheter easily while leaving the guide wire in the lesion; and it is also possible to shorten the surgical period and reduce the number of devices used.
Exemplified above is a balloon catheter having a balloon in the distal end side of the distal-end-sided shaft, but the characteristics of the OTW and RX catheters are not limited to the balloon catheter, and are also common to penetrating catheters for stricture penetration, injection catheters for administration of a treatment substance, and other catheters. The present invention relates to such a RX catheter.
Various methods for improving the convenience in operating the RX catheter are disclosed.
Patent Document 1 discloses a balloon dilation RX catheter having an opening of guide wire lumen in the region between the middle region and the base region, wherein, when the guide wire is placed in the guide wire lumen, the catheter is supported thereby continuously over the entire length in the length direction.
The catheter disclosed in the prior art is favorable in convenience of operation, because the catheter is supported continuously in the longitudinal direction when the guide wire is placed, but disadvantageously, the change in rigidity of the catheter itself in the length direction is discontinuous, and thus, when the catheter is inserted into the body from outside along the guide wire, the catheter is easily broken at the connection region between the middle region and the base region, and thus, it is extremely low in the convenience of operation.
Alternatively, Patent Document 2 discloses an intravascular catheter, comprising a metal-tube main shaft, a balloon, a plastic shaft region between the main shaft and the balloon, an intermediate unit not harder than the main shaft region that is connected to the main shaft and extending in the plastic shaft region in the proximal terminal direction, and a guide wire lumen, wherein the inlet of the guide wire is formed at a position separated in the proximal terminal direction from the proximal terminal of the main shaft region.
The prior art discloses a catheter improved in slidability and shape compatibility; the convenience of operation when a catheter is inserted into the body along the guide wire from outside is also improved; but there is still a problem in production cost. Such a catheter demands an additional step of brazing, laser bonding, or the like for connecting the intermediate unit not harder than the main shaft region to the main shaft, causing problems of increase in production cost by installation of a large-scale facility, complication of processing, and others.
Yet alternatively, Patent Document 3 discloses a dilation catheter having a stylet allowing improvement in the compression strength of the catheter shaft and the transmission (insertion) efficiency of the force in the axial direction.
In this prior art, presence of the stylet leads to improvement in force transmission (insertion) in the axial direction and also in the convenience of operation when the catheter is inserted into the body along the guide wire from outside; but the catheter has a structure in which the proximal terminal of the stylet terminates at the hub unit including the proximal terminal region of catheter shaft; and thus, when it is a balloon catheter, the stylet is present in most of the inflation lumen, and disadvantageously, the response of the balloon to inflation and deflation becomes lower. Alternatively when the catheter is an injection catheter, the stylet is present in most of the infusion lumen (lumen for injection of a treatment substance), disadvantageously reducing the convenience of operation in injecting a treatment substance.
Patent Document 4 discloses a RX balloon catheter having a proximal-end-sided shaft of metal tube, having a structure in which the core wire for adjustment of flexibility is connected to the distal-end-sided shaft only in the area close to the proximal opening of the guide wire lumen.
In this prior art, the convenience of operation when a catheter is inserted into the body along a guide wire and the response of the balloon to inflation and deflation are improved, without complication of processing or increase in production cost. However, the catheter described in this prior art has a structure in which the core wire is connected to the distal-end-sided shaft only in the area close to the proximal opening of the guide wire lumen, and thus, it is not possible to exclude the possibility of the following shaft damage. Namely when the lubricity between the guide wire and the balloon catheter during use of the balloon catheter drops drastically, for example, by deposition of thrombus, if a force is applied to the proximal-end-sided shaft for sliding or withdrawal of the balloon catheter, a tension in the axial direction is applied to the balloon catheter itself. Although the possibility is quite low, there is still very small possibility that the proximal end of the distal-end-sided shaft is elongated and deformed by the tension and the proximal end of the core wire present in the proximal-end-sided shaft may move to the proximal end of the distal-end-sided shaft. Accordingly, there is still a possibility of the damage of the proximal end of the distal-end-sided shaft elongated or deformed by the proximal end of the core wire and the damage, for example of blood vessel, by the proximal end of the core wire penetrating through proximal end of the distal-end-sided shaft, although it is quite rare.    Patent Document 1: Japanese Examined Patent Publication No. 5-28634    Patent Document 2: Japanese Unexamined Patent Publication No. 6-507105    Patent Document 3: Japanese Unexamined Patent Publication No. 9-503411    Patent Document 4: Japanese Unexamined Patent Publication No. 2003-102841